If your ancestors were farm workers in the 1800s, and did not marry in May, check the birth date of their oldest child.
Most work contracts ran from May to May. Farm workers who planned on getting married, often married in May so they could then move in together and maybe lease their own farm.
When there was a baby on the way, it was customary to marry as soon as possible and not to wait until May. So if you find that your farming ancestors married in a different month, check the birth records to find out when they had their oldest child. In many cases, you will find that the bride was pregnant.